RTLS Special Features

Accuracy verification

Introduction

Starting from the server software version 2.7.31, Eliko RTLS has a positioning accuracy verification functionality, which allows users to benchmark the calculated tag coordinates against the known coordinates of pre-defined reference points within the tracking area. After defining reference points and saving them into the database, a user can navigate through the whole process either by using the Eliko RTLS Manager Web UI or by entering specific API commands every time when positioning accuracy verification is needed. The verification process by using the API commands is organized as follows:

1. Process initialization starting with the command LOAD_ANCHOR_COORDINATES and followed by the command DELETE_FRAME_COORDINATES, which clears the history of the previous measurements

2. If a user plans to insert all the reference points into the system at once, this is done by the command ADD_FRAME_COORDINATES. The maximum number of reference points allowed by the system is 20. Otherwise, if a user prefers a point-by point measurement by inserting the coordinates of each reference point separately, this step is skipped.

3. After all the reference points are inserted into the system, the measurement mode is initialized by the command COLLECT_POINTS with the serial number of the tag selected for verification measurements. If no reference point list has been inserted, i.e. measurements are done point-by-point,  this step is skipped.

4. The installation engineer moves the tag to each reference point in sequence and performs a measurement by entering the ADD_POINT command with the serial number of the tag selected for verification measurements. If measurements are done point-by-point, the tag serial number is also followed by the reference point X, Y and Z coordinates.

5. After the measurements in all reference points are done, the process is stopped by entering the ADD_POINT command without any arguments

6. The system then compares the known pre-measured coordinates with the UWB RTLS measured ones and gives the accuracy of the system (measurement alpha)

LOAD_ANCHOR_COORDINATES

The command LOAD_ANCHOR_COORDINATES must be called before accuracy verification.

Client sends:

$PEKIO,LOAD_ANCHOR_COORDINATES

If the request was successful, the system responds:

$PEKIO,OK

If there was an error while processing the request due to RTLS server software version incompatibility, the following response will be sent:

$PEKIO,CANNOT_UNDERSTAND

DELETE_FRAME_COORDINATES

This command needs to be sent to the system to clear the history of the previous accuracy verification measurements before starting the process.

Client sends:

$PEKIO,DELETE_FRAME_COORDINATES

If the request was successful, the system responds:

$PEKIO,OK

If there was an error while processing the request due to RTLS server software version incompatibility, the following response will be sent:

$PEKIO,CANNOT_UNDERSTAND

ADD_FRAME_COORDINATES

This command is used when measuring with predefined reference points to add coordinates of each reference point. Up to 20 reference points can be created for accuracy verification. If of a point-by-point measurement, this command is not used.

 Client sends:

$PEKIO,ADD_FRAME_COORDINATES,<parameter list>

<parameter list> is a comma-separated list with the following fields:

A full example of client request would be:

$PEKIO,ADD_FRAME_COORDINATES,15.27,6.78,3.25

If processing the request was successful, the system responds:

$PEKIO,OK

If there was an error while processing the request, the following response will be sent:

$PEKIO,NOT_GOOD,<error ID>

<error ID> can be one of the following:

COLLECT_POINTS

This command is used to initialize the measurement mode if all the reference points were previously inserted into the system by the command ADD_FRAME_COORDINATES. If of a point-by-point measurement, this command is not used.

Client sends:

$PEKIO,COLLECT_POINTS,<parameter list>

<parameter list> is a comma-separated list with the following fields:

A full example of client request would be:

$PEKIO,COLLECT_POINTS,0xBFA,3

If processing the request was successful, the system responds:

$PEKIO,OK

If there was an error while processing the request, the following response will be sent:

$PEKIO,NOT_GOOD,<error ID>

<error ID> can be one of the following:

ADD_POINT

This command is used by the accuracy verification feature in three formats:

• To run an accuracy verification measurement in each reference point in case of a point-by-point measurement, i.e. no reference points were previously inserted into the system. In this format, the serial number of the tag used for the measurements is followed by X, Y and Z coordinates of each reference point

• To run an accuracy verification measurement in each reference point if all reference points were previously inserted into the system. In this format, only the serial number of the tag used for the measurements needs to be entered as a parameter; no coordinate values are used to run measurements and, therefore, the tag serial number is followed by three consecutive commas.

• To finalize the accuracy verification process and call the measurement statistics report from the system after all measurements are done. In this format, no parameters are used with the command, i.e. it is simply followed by four consecutive commas

Client sends:

$PEKIO,ADD_POINT,<parameter list>

<parameter list> is a comma-separated list with the following fields:

A full example of client request for a measurement with pre-defined reference points would be:

$PEKIO,ADD_POINT,0xBFA,,,

A full example of client request in case of a point-by-point measurement would be:

$PEKIO,ADD_POINT,0xBFA,5.23,12.74,3.5

A full example of client request in case of finalizing the accuracy verification process and calling the measurement statistics report would be:

$PEKIO,ADD_POINT,,,,

If processing the measurement request was successful, the system responds:

$PEKIO,OK

When the accuracy verification process has been successful, the system responds with a measurement statistics report that consists of measurement results for each reference point (one line per reference point) followed by the average coordinate difference value and terminated by the EOF marker:

$PEKIO,POINT,<parameter list>

$PEKIO,POINT,<parameter list>

…

$PEKIO,D_AVERAGE,<parameter>

$PEKIO,EOF

<parameter list> returned with POINT is a comma-separated list with the following fields:

Field name	Explanation	Example
Actually measured coordinates	X, Y and Z coordinates measured by the tag in the reference point. May have 6 digits after the comma, in this example trunked to 2 for a more simplified visualization.	21.54,1.56,0.68
Configured coordinates	X, Y and Z coordinates entered by the user for the reference point before measurements. May have 6 digits after the comma, in this example trunked to 2 for a more simplified visualization.	21.19,3.66,0.72
Coordinate difference	The difference between measured and configured X, Y and Z coordinates calculated as:	2.132039

<parameter> returned with D_AVERAGE has the following meaning:

Field name	Explanation	Example
Average coordinate difference	The average value of differences between defined and actually measured X, Y and Z coordinates of all reference points. Calculated as: Where N is the number of reference points.	1.668693

A full example of measurement statistics report would be:

$PEKIO,POINT,21.54,1.56,0.68,21.19,3.66,0.72,2.132039

$PEKIO,POINT,19.26,5.21,-0.16,19.54,6.72,0.72,1.772986

$PEKIO,POINT,20.90,5.99,0.61,21.72,6.72,0.72,1.101054

$PEKIO,D_AVERAGE,1.668693

$PEKIO,EOF

If there was an error while processing the request, the following response will be sent:

$PEKIO,NOT_GOOD,<error ID>

<error ID> can be one of the following:

Anchor self-positioning

Introduction

The anchor self-positioning feature helps to set up the Eliko RTLS without a need to manually measure all the anchors' coordinates. Instead, the system calculates the anchor coordinates using 3 reference points in the tracking area. The system uses distance measurement reports sent by the tags in each of these three known reference points. This is useful for a fast rollout of an RTLS setup of up to 6 anchors.

The anchor self-positioning process is organized as follows:

• Anchors are placed in the tracking area, no coordinate measurement is needed

• 3 reference points with known (measured) coordinates are selected in the tracking area

• 3 main anchors and 1 orientation anchor are defined by the command CALCULATE_ANCHOR_COORDINATES

• A tag is consecutively placed in 3 reference points and the SET_FRAME_POINT command is used for coordinate input in each reference point. This concludes the setup process during which the anchors network has gone through self-positioning and the RTLS is ready for use.

For more information about the anchor self-positioning feature, please refer to the retaled chapter in the Eliko Knowledge Hub.

CALCULATE_ANCHOR_COORDINATES

This command sets up a preliminary coordinate system. Client sends:

$PEKIO,CALCULATE_ANCHOR_COORDINATES,<parameter list>,0,0,0,0,0,0

<parameter list> is a comma-separated list with the following fields:

A full example of client request would be:

$PEKIO,CALCULATE_ANCHOR_COORDINATES,0xCC3,0xCB6,0xCB4,0xCC6,0,0,0,0,0,0

The RTLS Server then responds with a sequence of A_TO_A messages indicating the coordinate calculation progress, which may take ca 1 minute time. The penultimate message in the sequence is:

$PEKIO,A_TO_A,DB_SAVE_DONE

If processing the request was successful, the last message of the RTLS Server response is:

$PEKIO,OK

If there was an error while processing the request, the following response will be sent on the last line:

$PEKIO,NOT_GOOD,<error ID>

<error ID> can be one of the following:

SET_FRAME_POINT

This command aligns the RTLS coordinate system to an external coordinate system by using three reference points and is executed in each reference point. Client sends:

$PEKIO,SET_FRAME_POINT,<parameter list>

<parameter list> is a comma-separated list with the following fields:

A full example of client request would be:

$PEKIO,SET_FRAME_POINT,2,0x000F42,-3.0,2.8,1.15

If processing the request was successful, the system responds:

$PEKIO,OK

If there was an error while processing the request, the following response will be sent:

$PEKIO,NOT_GOOD,<error ID>

<error ID> can be one of the following: